Tony Abbott's department is working overtime to cope with an avalanche of correspondence after the Prime Minister put in place new rules that require a direct response from the highest political office in the land.

About 40 staff in the Department of Prime Minister and Cabinet volunteered to work last Saturday to try and clear the backlog of letters and emails from the public.

Copies of emails sent by department head Ian Watt to staff, leaked to Fairfax Media, reveal growing concern as far back as February over the ''resources pressure for us all''.

At the time, Mr Watt wrote that while letters to the Prime Minister over a particular issue or policy were usually referred to the relevant department, a direct response from the Prime Minister's department was ''a high priority for the PM and outcomes are regularly monitored [by] the office''.

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''The Prime Minister has requested changes to the handling arrangements of this correspondence, seeking prompt and appropriate responses to all writers. To the extent possible, he would like these replies to come from his portfolio''.

On Friday, Mr Watt praised staff who had volunteered to work on Saturday to cope with the letters.

''I am particularly impressed by the dedication of staff in the department who are willing to give up their Saturday to assist with the back log of ministerial correspondence,'' Mr Watt wrote.

''Within 24 hours of the request going out … almost 40 volunteers who will assist in ensuring letters and emails from members of the public are responded to in a timely way, which is a high priority for the Prime Minister.''